Humans can become confused and disoriented
- and even a little queasy - in an alien world where up and down
have no meaning. It can be difficult feeling Lost in Space.

by Patrick Barry and Dr Tony
Phillips

Imagine waking up, startled by the bright
flash of a cosmic ray inside your eyes. Groggy from sleep, you wonder
... which way is up? And where are my arms and legs? Throw
in a dash of vertigo and occasional mild illusions, and you're beginning
to sense what it can be like to live in orbit.

Of course, it's not always so bad - otherwise no
one would want to become an astronaut! Nevertheless, first-time
space travellers can be surprised by some very unearthly sensations
that can confuse and amuse the astronauts who feel them.

Consider, for example, "up" and "down." On Earth
we always know which way is up because gravity tells us. Sensors
in the inner ear, which are part of the body's vestibular system,
can feel the pull of gravity. They signal the brain with information
about our body's orientation.

In space, however, the vestibular system doesn't
sense the familiar pull of gravity. The world can suddenly seem
topsy-turvy.

Former shuttle astronaut Robert Parker recalls:
"One of the questions they asked us during our first flight was,
'Close your eyes ... now, how do you determine up?'" With his eyes
closed, he couldn't tell. Up and down had vanished.

Another astronaut reported a strange experience
when he woke up one day in orbit. As he opened his eyes the room
was rotating around him!

The vestibular system is a fluid-filled network
of canals and chambers deep within the human ear that help
us keep our balance and sense which way is up.

Or so it seemed.

Space travellers in science fiction
rarely have such problems. On Star Trek's USS Enterprise,
for example, artificial gravity provides direction cues for the
crew. Captain Kirk never gets out of bed upside-down.

Without artificial gravity, however,
the designers of the real-life International Space Station and the
Space Shuttle must rely on different tricks to establish a common
sense of "up". For example, all of the modules on the ISS have a
consistent "up" orientation. And the writing on the walls points
in the same direction, too.

Shuttle mission specialist John-David
Bartoe remembers his first days in orbit: "I followed the advice
from my commander, Gordon Fullerton. He recommended that for the
first few days we always keep ourselves oriented up with respect
to the writing on the walls and with respect to the other crew members.
This worked fine for me.

"After day two I was more adventurous
and would turn upside down for fun - I had no problem!"

The vestibular system isn't the only
one affected by the absence of weight. The proprioceptive system
- that is, nerves in the body's joints and muscles that tell us
where our arms and legs are without having to look - can also be
fooled. Without the stresses in the joints usually caused by the
pull of gravity, this sense is sometimes dampened.

"The first night in space when I was drifting
off to sleep," recalled one Apollo astronaut, "I suddenly realized
that I had lost track of ... my arms and legs. For all my mind could
tell, my limbs were not there. However, with a conscious command for
an arm or leg to move, it instantly reappeared - only to disappear
again when I relaxed."

Another astronaut from the Gemini program reported
waking in the dark during a mission and seeing a disembodied glow-in-the-dark
watch floating in front of him. Where had it come from? He realized
moments later that the watch was around his own wrist.

These sorts of mismatches between what the eyes
see and what the body feels can trigger a malady called "space sickness."
Scientists think it's much like "car sickness," which you can get
right here on Earth by trying to read in a moving car. The inner
ear detects the motion of the car but the eyes - staring at a page
filled with unmoving words - do not.

"When people go up into space, many will immediately
get space sickness," says Dr. Victor Schneider, research medical
officer for NASA's Biomedical Research and Countermeasures Program.
While a few astronauts are apparently immune, most can experience
symptoms ranging from mild headaches to vertigo and nausea. In extreme
cases prolonged vomiting can make an astronaut dehydrated and malnourished.

Before
blasting off for space, astronauts try to acclimate their
bodies to space by riding the "vomit comet" - a KC-135
airplane that flies parabolic arcs to create short periods
of weightlessness

Fortunately, the brain quickly adapts.
It learns to trust the eyes and reprograms signals from the vestibular
system to reconcile the mismatch. "Space sickness relieves itself
after about 3 days, although individual astronauts and cosmonauts
may have a relapse at any time during their mission," Schneider says.

Indeed, space sickness is capricious - when it
will happen and who will get it can be hard to predict. Some astronauts
who show an exceptional tolerance to motion sickness when flying
jets suffer the worst symptoms upon arriving in space. "This occurs
on Earth as well," adds Schneider. "For example, gymnasts who perform
acrobatics and do not get motion sick may get sick on a roller coaster
or in the back seat of a moving car."

Figuring out how to prevent space sickness - and
how to treat it when it happens - is a high priority for NASA.
For that reason, in 1997, NASA helped establish the National
Space Biomedical Research Institute
(NSBRI) where researchers
study how humans adapt to weightlessness and develop "countermeasures"
against maladies like space sickness.

Much of the NSBRI's research is conducted on Earth
and can directly benefit millions of patients that never leave our
planet. For example, an estimated two million American adults suffer
chronic impairment from dizziness or difficulty with balance. And
nearly one quarter of all emergency room visits include a complaint
of dizziness. Figuring out why we're mixed up and lost in space
can have some down-to-Earth benefits!